U.S. patent application Ser. No. 12/916,984 (which has been incorporated herein by reference) has been published as United States Patent Application Publication No. 2011/0100874. The reader is presumed to be familiar with the disclosure of this published application. This published application will be referred to herein as the “'874 application.”
The demand for energy (and the hydrocarbons from which that energy is derived) is continually rising. However, hydrocarbon raw materials used to provide this energy often contain difficult-to-remove sulfur and metals. For example, sulfur can cause air pollution and can poison catalysts designed to remove hydrocarbons and nitrogen oxide from motor vehicle exhaust, necessitating the need for expensive processes used to remove the sulfur from the hydrocarbon raw materials before it is allowed to be used as a fuel. Further, metals (such as heavy metals) are often found in the hydrocarbon raw materials. These heavy metals can poison catalysts that are typically utilized to remove the sulfur from hydrocarbons. To remove these metals, further processing of the hydrocarbons is required, thereby further increasing expenses.
Currently, there is an on-going search for new energy sources in order to reduce the United States' dependence on foreign oil. It has been hypothesized that extensive reserves of shale oil, which constitutes oil retorted from oil shale minerals, will play an increasingly significant role in meeting this country's future energy needs. In the U.S., over 1 trillion barrels of usable, reserve shale oil are found in a relatively small area known as the Green River Formation located in Colorado, Utah, and Wyoming. As the price of crude oil rises, these shale oil resources become more attractive as an alternative energy source. In order to utilize this resource, specific technical issues must be solved in order to allow such shale oil reserves to be used, in a cost effective manner, as hydrocarbon fuel. One issue associated with these materials is that they contain a relatively high level of nitrogen, sulfur and metals, which must be removed in order to allow this shale oil to function properly as a hydrocarbon fuel.
Other examples of potential hydrocarbon fuels that likewise require a removal of sulfur, nitrogen, or heavy metals are bitumen (which exists in ample quantities in Alberta, Canada) and heavy oils (such as are found in Venezuela).
The high level of nitrogen, sulfur, and heavy metals in shale oil, bitumen and heavy oil (which may collectively or individually be referred to as “oil feedstock”) makes processing these materials difficult. Typically, these oil feedstock materials are refined to remove the sulfur, nitrogen and heavy metals through a process known as “hydro-treating.” The hydro-treating process, as well as the potential problems of the hydro-treating process, are described in the '874 application.
Additionally, naphthenic acids must be removed from many organic streams that are produced by refineries. Naphthenic acids (“NAPs”) are carboxylic acids present in petroleum crude or various refinery streams. These acids are responsible for corrosion in refineries. A common measure of acidity of petroleum is called the Total Acid Number (“TAN”) value and is defined as the milligrams (mg) of potassium hydroxide needed to neutralize the acid in one gram of the petroleum material. (Other acids found in the oil feedstock may also contribute to the TAN value). All petroleum streams with TAN >1 are called high TAN. NAPs are a mixture of many different compounds and cannot be separated via distillation. Moreover high TAN crudes are discounted over Brent Crude prices. For example, Doba crude with a TAN of 4.7 is discounted by $19 per barrel on a base price of $80 for Brent crude.
NAPs boil in the same range as that of kerosene/jet fuel. (However, kerosene/jet fuels have very stringent TAN specifications.) Attempting to neutralize these acids using aqueous caustic or other bases form salts. These salts in presence of water, lead to formation of stable emulsions. Additional methodologies of NAP reduction include hydrotreating or decarboxylation that are both destructive methodologies and the NAPs cannot be recovered using these methods. Solvent extraction or adsorption methodologies lead to high costs and energy usage for sorbent regeneration or solvent boiling.
NAPs in the oil feedstock can also cause corrosion of the pipes that are used to transport the oil feedstock. Accordingly, a method for preventing the corrosion of pipes that are used to process/transport oil materials that have high NAP values is needed.
Corrosion of ferrous material such as steel or stainless steel is a problem in oil pipelines, oil storage tanks, and the piping and process equipment at oil refineries, especially if such piping is used with materials that have a high TAN value. Oil refinery operators often limit how much feed is allowed into the refinery that has a high TAN number because they know that their ferrous piping and process equipment will corrode more readily if the TAN number is too high. As a result, the price paid for petroleum feedstocks with higher TAN will be lower than the price paid for feedstocks with lower TAN. For the purposes of this document, the term “stainless steel” refers to ferrous material other than mild steel.